The Ventriculophasic Response Revisited: Analysis of Clinical Correlations Using a New Proposed Definition Derived in Pacemaker Patients

Abstract

The ventriculophasic response (VR) refers to shortening of atrial cycle length during heart block when a QRS complex is interposed between P waves. No formal quantitative definition has heretofore been proposed, nor have its potential clinical correlations been studied. We hypothesized that VR is present in selected patients who are distinguished by clinical features from those who lack VR. Pacing devices were temporarily programmed to VVI mode at 30 ppm as electrocardiogram and intracardiac electrograms were recorded at 50 mm/sec paper speed. We measured the percentage decrease in a P-P interval (A-A interval on the atrial electrogram) containing a QRS, compared to the preceding P-P interval. Left ventricular ejection fraction (LVEF) was measured by echocardiogram. Shortening of P-P interval was observed chiefly when the interposed QRS occurred early in the anticipated P-P interval (as judged by the preceding P-P interval). P-P shortening of 0% to 3% occurred randomly. Defining VR as being a >3% P-P interval shortening when an interposed QRS occurred in the first 60% of the anticipated P-P interval, we found that VR was present in 28 (55%) of our patients. It was quite reproducible, was more common in women (81% vs 37% of men; P = 0.004), and positively correlated with LVEF (r = 0.41, P = 0.004). It did not correlate with age, diabetes, or β-blocker use. Using our newly derived definition of VR, we found the phenomenon was present in 55% of our patients. It was reproducible and more commonly seen in women and patients with LVEF ≥40%.